Embryonic development of craniofacial structures requires a tightly orchestrated series of cellular and morphological events. These include regulation of cellular proliferation, growth, migration, and differentiation. The sensitivity of thse processes to perturbation is evident by the high incidence of human birth defects affecting the head and associated structures (~75% of all birth defects have a craniofacial component), most common of which is orofacial clefting (~1:600-1,000 live births). These defects will impart a significant decrease in quality of life on those afflicted and present a major economic burden associated with treatment. To better understand and ultimately prevent these disorders prenatally a precise understanding of genes controlling the aforementioned cellular processes during normal craniofacial development is required. To this end, through an ENU based mutagenesis screen, we have identified Mediator of ErbB2-driven cell motility 1 (Memo1) as a novel regulator of multiple aspects of craniofacial development, including appropriate formation of the skull-base and palate. Interestingly, most of the affected structures in Memo1enu/enu mutants are derived from the cranial neural crest cells, implicating a role for Memo1 within this embryonic stem-cell population. Previous studies identified Memo1 as an important component in modulating extracellular cues into intracellular responses, such as cellular migration and proliferation. However, Memo1-null embryos are early embryonic lethal, precluding any analysis of Memo1's role during craniofacial development. Our Memo1 ENU-allele thus provides a unique model to decipher Memo1's role during these processes. Our general goal is to precisely characterize the mechanistic role of Memo1 during craniofacial development using two Aims. (AIM 1) First, by combining our Memo1 ENU-allele with a Memo1 null-allele, we will generate an allelic series, serving as a convenient genetic model system to dissect Memo1's cellular role during craniofacial development. The resultant allelic combinations will be utilized for analysis o gross craniofacial development and cranial neural crest cell biology, including a more detailed in vitro examination of neural crest cell migration. (AIM 2) Secondly, because Memo1 is expressed in multiple craniofacial tissues, we will generate a conditional allele of Memo1 allowing its tissu specific deletion. Given the majority of the defects in our ENU- mutant are found in structures derived from the cranial neural crest cells, we will specifically assess the cell autonomous requirements of Memo1 in this tissue by generating mutants with a neural crest specific deletion of Memo1, and thoroughly characterize how this impacts craniofacial development. In summary, Memo1 has only recently been linked with face formation but further characterization of this gene is likely to generate insight into the broader gene network responsible for normal human facial formation. In the long-term, the work proposed will contribute to a more detailed understanding of processes involved in craniofacial development, providing a clearer path towards detection and prevention of craniofacial disorders.